There may be various types of diseases in fishes. The body of a healthy fish is slimy and its colour is bright. If the original colour is changed or discoloured it is to be understood that there is some sort of illness or trouble in the fish. The health of the fish is to be examined once or twice a month by catching them with driftnet, because by checking the health of fish, treatment might be given if required. The fishes may also become ill due to scarcity of food, insufficient or unsuitable food lack of oxygen, fluctuation of temperature, attack of parasites etc. Besides this they may be ill due to attack of different species of protozoa, round worms leeches and lice. Some important diseases of fishes are as follows.

(I) Gill rot disease: This disease is caused by the attack of a kind of fungi. I n this disease the blood circulation is disturbed in the gills which ultimately rots As a result the respiratory process is affected and the fish dies. This diseae, may become epidemic when the pond is full of rotten or half rotted organic matters and have an excessive heat.

Treatment: The pond has to be treated adequately with lime and the fishes have to be supplied with artificial food.

(II) Fin or tail rot disease: This disease is caused by the attack of a bacteria. Due to this disease white spots appear and the fin becomes blunt

Treatment: 2000 part water and one part of copper Sulfate are to be mixed, and then if the fish is kept in it for one minute, then it get might cured.

(III) White speckle disease: Due to attack of a kind of protozoa minute speckles appear on the body of fishes.

Treatment: For its treatment the pond has to be purified with salt or powdered rock lime. The fish becomes free from this germ if it is kept submerged for half an hour in 100 parts water with 3 parts salt in it.

(IV) Fish lice: The name of the fish louse is Argulas. This louse is oval in shape and slightly flat. This louse remains attached with the skin below the scale with the help of a pair of suckers on the ventral side. As a result th scales become detached and the body becomes uncovered. This affects the health of the fish.

Treatments: (i) The affected fishes are to be transferred from one pond to other (ii) water of the pond is to be removed and the pond has to be dried for least 24 hours in the sun, (iii) The pond water has to be sprayed with 10-30 grams of lime per litre.

(V) Leech of fish: In the body of leech of fish, there are two suckers. With one sucker leech remains clung with the fish and with the other it sucks the blood of the fish.

Treatment: The leech dies if the affected fish is kept in water having 100 parts water and 25 parts of salt for 15 minutes.